最新刊期
卷 ， 期 2 ， 2008
- 摘要：A novel alternate routing algorithm is proposed on the basis of balanced load of links and tabu-search and the optimization of solution search and the link load variance and congestion realized.After the routing is chosen,the wavelengths are assigned to each optical channel by using the first-fit method on the ’longest first’ principle.Different routing algorithms are simulated under the static traffic pattern of the ring and mesh networks.The simulation results indicate that using the new algorithm,the best routing can be arranged by the full use of the network resources,thus effectively reducing the demand for wavelengths.关键词：WDM optical network;alternate routing;link load variance;congestion;tabu-search
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发布时间： - 摘要：Five typical traffic routing assignment algorithms are introduced,namely,Shortest Routing Algorithm（SRA）,Splitting Loading Algorithm（SLA）,Balance Algorithm（BA）,Demand Routing Algorithm（DRA） and Non-Splitting Loading Algorithm（NSLA）.By using a uniform mathematical model,a method is presented for the analysis of and comparison between these five algorithms and the features of 4 of them and their applications in different traffic models obtained by computations.The results show that all these 4 algorithms can reduce the ring capacity assignment to a certain extent.关键词：optical ring network;traffic optimization;assignment algorithm;improvement factor
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发布时间： - 摘要：As an next generation optical network technology,T-MPLS needs to satisfy the requirements of the customers for QoS.In this text,the definition of QoS is introduced first.Then,the methods for achieving QoS are described,the flow supervision and shaping by using leak algorithm specifically analyzed,and the way of application scheduling explained.Finally,simulation tests are performed for QoS improvement.关键词：QoS;T-MPLS;SLA
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发布时间： - 摘要：Frame synchronization is an important part of PCM equipment.In this text,a synchronous state machine-based frame synchronization detection circuit is designed,which has front and rear protection for frame synchronization and protection for CRC multi-frame synchronization,greatly reducing the probabilities of leak and false synchronizations and providing CRC error detection.It can be integrated into one FPGA chip and used for the frame synchronization and timing in the receiver side of digital communication systems.关键词：frame synchronization;state machine;FPGA;circuit design
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发布时间： - 摘要：Trellis Coded Modulation（TCM）is introduced into PPM to investigate the error performance improvement in optical Pulse Position Modulation（PPM） systems.Theoretical deduction and MATLAB simulation and comparisons of 8T-PPM with 16 PPM and 16T-PPM with 32 PPM respectively,produce the following results.When the bandwidth is kept constant,8T-PPM and 16 PPM have the same information rate,but the error performance of the former is better than the latter,up to 4.8 dB at the maximum.On the other hand,the information rate of 16T-PPM is 1.2 times that of 32PPM,but it has better error performance,up to 3.4 dB at the most.These results prove that the introduction of TCM into PPM does effectively improve the error performance of the system.关键词：PPM;TCM;MATLAB;error rate
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发布时间： - 摘要：On the basis of the analysis of cross-transmission characteristics of the Long-Period fiber Grating（LPG）,we find that superstructured LPG has a cross-transmission spectrum similar to the reflection spectrum of SuperStructured Fiber Bragg Grating（SSFBG）.By utilizing the coupling between the fundamental mode and the inner cladding mode coexisting in the Dispersion Compensating Fiber（DCF）,superstructured LPG-based encoder/decoder for time-spread phase-coded OCDMA system can be realized.Simulation results show that identical encoding/decoding performance can be achieved with superstructured LPG.and superstructured FBG.关键词：optical communication;OCDMA;SuperStructured Long Period Grating（SSLPG）;time-spread phase coding
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发布时间： - 摘要：A novel ring topology-based optical CDMA access network is proposed and its model and performances analyzed.A self-interference suppression scheme based on the cyclical frequency domain coding technology is designed for the ring network,which is analyzed and discussed.The tests prove that the network allows all users to communicate simultaneously and the network efficiency and flexibility are improved.关键词：OCDMA;all-optical network;self-interference
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发布时间： - 摘要：As optical receivers in 2D asynchronous OCDMA systems are subject to various noise interferences and to Multiple Address Interference（MAI） among the users,optical receivers with double Optical Hard-Limiters（OHL） are used to optimize the system transmission performance.In this paper,the effects of the threshold,the number of users and the incident optical power on the system BER are numerically analyzed.The results show that 2D asynchronous OCDMA systems with double OHL have much lower BER than those with one or no OHL and MAI is almost reduced to zero.关键词：2D asynchronous OCDMA system;MAI;receiver noise;OHL
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发布时间： - 摘要：As a part of the conference control in Multimedia Conferencing Systems（MCS）,floor control is used to coordinate the access to the shared resources among the participants,which has a direct bearing upon the QoS of the system.In this paper,the floor control in SIP-based MCS is realized in the architecture of JAIN SIP by using the scalability of the Session Initiation Protocol（SIP）,which is characteristic of diversity in the way of control and adaptability to distributed systems.The test results show that the system design is rational and the delay is tolerable.关键词：floor control;conference control;SIP
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发布时间： - 摘要：This paper first introduces the basic concept that is relavant to the receiving sensitivity of GSM systems and cable access frequency shifting repeaters.Then,it calculates the receiving sensitivity of Base Transceiver Stations（BTS） and repeaters under extreme conditions,and analyzes the influences of different repeater uplink gain distributions on the sensitivity of the entire system.Finally,it presents the rational distribution of the link gains of repeaters in project applications for the optimization of the system sensibility.关键词：repeater;noise figure;sensitivity
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发布时间： - 摘要：In the future,session based services and non-session based services are sure to co-exist in the same NGN,while diversified servers and fine control of the non-session based services must be simultaneously available to ensure the QoS of the entire NGN.In this paper,three co-working modes between the Resource and Admission Control Subsystem（RACS） and the Deep Packet Inspection（DPI） system in NGN are presented and their advantages and disadvantages discussed and analyzed,and it is pointed out that exclusive identification and control modes are suitable for telecom providers to deploy DPI systems in NGN.关键词：NGN;DPI;RACS
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发布时间： - 摘要：As endless problems and potential hidden dangers of security exist at the network layer of mobile communication networks,virus prevention and elimination has become very important.In this paper,real cases are cited to explain the security crisis in current mobile communication networks so as to heighten mobile communication users’ awareness of cell phone viruses and solutions to the security system of mobile communication network explained,i.e.preventive measures are to be taken at both the terminal side and the network side.关键词：mobile communication network security;cell phone virus;MMS virus;mobile operation system;application service/network access control
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发布时间： - 摘要：The propagation characteristics of chirped Gaussian pulses in fibers with 5 different group dispersion profiles are theoretically deduced and the effects of the initial chirps on the pulse width discussed.Compared with conventional Single Mode Fibers（SMF）,the pulse broadening in these five Dispersion-Decreasing Fibers（DDF） is effectively restrained to be slow with fairly big differences among themselves.As for the effects of the initial chirps on the pulses,when β2c>0,the pulse broadening is faster than that without chirps,while when β2c <0,the pulses are fast broadened after an initial process of narrowing.关键词：group dispersion profile;DDF;initial chirp;broadening factor
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发布时间： - 摘要：The design of wavelength tuning and stability control of tunable lasers is introduced and its feasibility verified by tests.The design scheme consists of temperature control,bias current control and wavelength locker circuits.The temperature control circuit is used for cursory tuning,the bias current circuit for fine tuning and the wavelength locker circuit for feedback of external temperature variations.It is applicable to the design of the driver circuit of the temperature control-based tunable DFB laser.关键词：wavelength tuning;stability control;Thermo-Electric Cooler（TEC）;wavelength locker
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发布时间： - 摘要：The Wavelength Dependent Loss（WDL） formula for the reflection-type Variable Optical Attenuator（VOA） based on Micro-Electro-Mechanical Systems（MEMS） is deduced by using matrix optics in connection with Gauss beam coupling.Such factors that are related to WDL as the air gap length d1 between the dual fiber pigtail and C-Lens,the lens length d2 and the refractive index and the curvature radius of C-Lens are analyzed in detail and numerical simulations performed respectively.The resulted key factors have major significance to the development of the MEMS-based reflection-type VOA.关键词：MEMS;WDL;matrix optics;VOA;Gaussian beam
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发布时间： - 摘要：Effects of fiber length selection on the gain spectrum shape of fiber-optic parametric amplifiers with high nonlinear fiber are studied.The results show that when other parameters are constant,different length selections enormously alter the shape of the spectrum.Finally,an optimum method is presented for the choice of the fiber length and effective performance improvement by using this method is verified by numerical simulation.关键词：fiber parametric amplifier;double pump;high nonlinear fiber
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发布时间： - 摘要：In this paper,an anti-reflection coaxial LD Transistor Outline（TO）-CAN without optical isolator is discussed,which is used to realize E/O transformation and anti-reflection of the LD by adopting the existing chip placing and gluing processes to assembly LD chip,polarizer and λ/4 wave plate in TO-Header.Both theoretical analysis and test results have verified its effectiveness and practical applicability.关键词：polarization;λ/4 wave plate;anti-reflection;isolation
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发布时间： - 摘要：Based on the nonlinear phase transmission characteristics of the ring resonator,a novel dynamic spectral filter structure is proposed,in which an all-pass ring resonator is coupled onto each arm of a symmetric Mach-Zehnder interferometer,realizing the dynamic filtering characteristics of the compound structure.Compared with the conventional symmetric Mach-Zehnder interferometer,this compound optical filter can be used to fabricate optical signal switches with much less power consumption.Thus,it will find important applications in increasing the switch and reducing the power consumption of phase modulators.关键词：ring resonator;Mach-Zehnder interferometer;spectral filter
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发布时间： - 摘要：Optical Feedback Self-Mixing Interferometry（OFSMI） is a newly emerging sensing and measurement technology.In this paper,for the measurement of the linewidth enhancement factor,large amounts of tests on semiconductor laser HL7851G are conducted by using this technology.The test result is basically in conformity with that by using the conventional linewidth measurement methods with a relative error of only 3.22%.Compared with the latter,OFSMI is a still more simple and effective measurement technique with the advantages of low cost and high precision.关键词：OFSMI;linewidth enhancement factor;Semiconductor laser
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发布时间： - 摘要：This paper first introduces the applications of fiber sensors and the structure of S-shaped fiber Acoustic Emission（AE） sensors.Then,it presents the interactions between the fiber AE sensor and ultrasonic waves and the theoretical analysis of the sensitivity of this type of sensors that are based on fiber Michelson interferometer.The result of the analysis is identical with that by Matlab simulation.关键词：Michelson interferometer;optical fiber;acoustic emission;sensor;sensitivity
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发布时间： - 摘要：A Fiber Raman Amplifier（FRA） working in C+L band is designed and implemented and the design of the pump driver circuit and the performances of 150 km EDFA+FRA hybrid transmission discussed.The experimental results indicate that the driver circuit operation is stable and reliable and the BER will not be markedly improved when the Raman amplifier gain is lower than 5 dB.The experiment provides a guide to the gain configuration in EDFA+FRA hybrid transmission systems.关键词：FRA;EDFA;power cost
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